Transcript Physical Oceanography Notes

Marine Science
Day 1: Atmospheric Circulation
Objectives:
 What is physical oceanography?
 What are the layers of the atmosphere?
 Explain how the surface of the Earth is heated.
 What are convection cells?
 What is the Coriolis Effect?
 Explain the affect of the Coriolis Effect on global wind
patterns.
 Explain how land masses affect global wind patterns
 Explain the difference between anabatic and katabatic
winds.
Physical Oceanography
 The study of physics within the marine environment.
 This includes:
 Sound
 Waves
 Currents
 Tides
 Light
 How the oceans influence weather and climate
Atmosphere
 The atmosphere is a mixture of gasses that
extends about 90 km from the Earth’s surface
 Differences in the heating of the atmosphere
at different latitudes sets the gasses in
motion… creating wind
 Layers of the atmosphere:
 Trophosphere
 Stratosphere
 Mesosphere
 Thermosphere
 The atmosphere is composed of:
 Nitrogen 78%
 Oxygen 21 %
 Inert Gasses (argon, helium, neon) 1%
 Carbon Dioxide (0.03)
kidsgeo.com
http://forces.si.ed
u/atmosphere/04_
00_01.html
Troposphere
 Lowest Layer
 Extends from the surface of the earth to an altitude of
about 12 km
 Temperature decreases with altitude at a rate of
approximately -10oC for each 1000m of elevation
 Where weather happens
Stratosphere
 Where the ozone layer floats
 Ozone Layer: Layer of O3 in
the stratosphere that shields
life from harmful ultraviolet
radiation from the sun
 Commercial airliners fly in
this layer
 From 12 to 50 km above Earth’s
surface
 Temperature increases with
altitude because the ozone
layer (O3) absorbs UV
radiation from the sun (heat)
theozonehole.com
Mesosphere
 From 50-80 km above Earth’s surface
 Temperature decreases as altitude increases
 Space debris begins to burn as it enters the
mesosphere… shooting stars blaze
Thermosphere
 From 82-640 km above the Earth’s surface
 Temperature rises
 Northern and Southern lights occur here
greenlandkid.com
Heating of the Earth’s Surface
 Solar radiation from the sun heats the Earth’s surface
 When the radiation hits Earth it is reflected, absorbed,
or reradiated.
Heating of the Earth’s Surface
 The intensity of solar radiation varies with latitude
virtualskies.arc.nasa.gov
Heat Budget
 More intense sunlight reaches the equator and the
intensity of solar radiation decreases towards to the
poles…
 At high latitudes the same amount of sunlight passes
through the atmosphere but the same amount of
sunlight is spread over a larger area
 To maintain a stable long term temperature, the Earth
must loose as much heat as it gains
 Excessive heat from the tropics tends to move to higher
latitudes by winds and ocean currents
Heat Budget
Formation of Convection Cells
Non-Rotating Earth
 Equator receives more heat
and has more warm moist air
(less dense)
 As this moist air rises this
creates an area of low
pressure
 When moist air rises it
condenses forming
precipitation
 The now dry air flows north
or south (depending on the
hemisphere) and sinks back
down at the poles …. Then
back to the equator… creating
a large convection cells
Formation of Convection Cells
Rotating Earth
 The Earth rotates and moves in
an easterly direction at a speed
of 1674km/hr at the equator
 The rotation of the Earth affects
the movements of the
atmosphere, the ocean, and any
other object not directly
attached to Earth
 Coriolis Effect: Deflection of
objects in movement not
directly attached to Earth
theozonehole.com
mind42.com
Surface Wind Bands
oneonta.edu
Effects of Continents and Seasons
 Large land masses modify the atmosphere
 Land masses have a lower heat capacity than water so
they absorb and lose heat faster – changes temperature
faster
 70% of land masses are in the northern hemisphere
 During the summer, land is warmer than the ocean,
causing a low pressure area over land (hot air rises) so
there is a continuous low pressure area between 0-60
degrees north
 During the winter, land is cooler than the oceans,
causing a high pressure area over land (cold air sinks)
Local
Effects
 Land warms faster during the day and as this warm air
rises it is replaced by air from over the ocean creating
an on-shore breeze / sea breeze (anabatic wind)
 At night, the air over land cools faster (sinks) than the
ocean, and air flows out toward the ocean creating an
off-shore breeze (katabatic wind)
 This typically creates rain on the windward side of
islands…
nc-climate.ncsu.edu
Atmosphere Video Clip
Day 2: Hurricanes
Objectives:
 What are hurricanes?
 Explain hurricane formation?
 How are hurricanes measured?
 Where do hurricanes get their name?
environment.nationalgeographic.com
Hurricanes
 Hurricanes are low pressure systems with winds greater than 74mph
 Named for the location in which they are occurring:
 Hurricanes are defined as storms over the North Atlantic or the
Caribbean
 In the western Pacific Ocean, hurricanes are known as typhoons.
 Cyclones are hurricanes over the Indian Ocean.
 Hurricane Formation
 Form over warm tropical waters ( sea surface temps greater than 27oC)
 Low pressure cells that occur in latitudes higher than 5o are set into a
circular motion by the Coriolis Effect – this causes a circular pattern
(counterclockwise in the northern hemisphere)
 As the storm grows, the winds evaporate more water (and heat) which
fuels the storm and creates a column of fast moving air
 Hurricanes dissipate/stop when they travel over land because they lose
energy
spaceplace.nasa.gov
windows2universe.org
Hurricane Development
 Tropical Disturbance: Group of thunderstorms with
very little wind circulation
 Tropical Depression: Storm with wind speeds up to
20 to 34 miles per hour
 Tropical Storm: Storm with wind speeds reach 35-64
miles per hour.
 Hurricane: When wind speeds reach 74 miles per
hour or greater
Hurricane Formation=
http://news.bbc.co.uk/2/hi/science/nature/4588149.st
m
Hurricane Development
bom.gov.au
Measuring Hurricanes
 Saffir-Simpson Scale. Scale that measures wind speed and air pressure of a hurricane.
 Category 1- winds 74-95 mph, 64-82 kt, 119-153 km/h
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Very dangerous winds will produce some damage: Well-constructed frame homes could
have damage to roof, shingles, vinyl siding and gutters. Branches of trees will snap, shallowly
rooted trees may be uprooted. Power outages could last a few to several days.
Category 2 - winds 96-110 mph, 83-95 kt, 154-177 km/h
Extremely dangerous winds will cause extensive damage: Well-constructed frame homes
could sustain major roof and siding damage. Shallowly rooted trees will be uprooted and block
numerous roads. Near-total power loss is expected - outages that could last from several days to
weeks.
Category 3 (major)- winds 111-129 mph, 96-112 kt, 178-208 km/h
Devastating damage will occur: Well-built framed homes may incur major damage or
removal of roof decking and gable ends. Many trees will be snapped or uprooted, blocking
numerous roads. Electricity and water will be unavailable for several days to weeks after the
storm passes.
Category 4 (major) – winds 130-156 mph, 113-136 kt, 209-251 km/h
Catastrophic damage will occur: Well-built framed homes can sustain severe damage with
loss of most of the roof structure and/or some exterior walls. Most trees will be snapped or
uprooted and power poles downed. Power outages will last weeks to possibly months. Most of
the area will be uninhabitable for weeks or months.
Category 5 (major) - winds 157 mph or higher, 137 kt or higher, 252 km/h or higher
Catastrophic damage will occur: A high percentage of framed homes will be destroyed, with
total roof failure and wall collapse. Fallen trees and power poles will isolate residential areas.
Power outages will last for weeks to possibly months. Most of the area will be uninhabitable for
weeks or months.
Hurricane Facts
 Hurricanes may have a diameter of 400 to 500 miles (640-800
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kilometers).
The “eye” (center) of a hurricane can be up to 20 miles (32 km)
across. The weather in the “eye” is surprisingly calm with low
winds and clear skies.
Hurricanes hit land with tremendous force, bringing huge waves
and heavy rain.
Many hurricanes cause severe flooding.
About 90 percent of the deaths that occur during hurricanes
result from drowning in floods.
The world’s worst hurricane (for loss of life) took place in 1970 in
Bangladesh. That hurricane created a flood that killed more than
one million people.
Thunderstorms often form within hurricanes and produce
tornadoes.
Damage from Hurricanes
boston.com
soest.hawaii.edu
sitemaker.umich.edu
uta.edu
Hurricanes in Media Literacy
 Movie
 Raging Planet – Hurricane
 Hurricane Katrina - National Geographic
geology.com
Tracking Hurricanes
Hugo and Katrina…
 Hurricane Tracking Video Clip
 Hurricane Lab
Day 3: Oceanic Circulation
Objectives:
 What are the two main types of ocean circulations?
 Explain the difference between upwelling and
downwelling.
 What are eddies?
 What is a wave?
 Label the parts of a wave.
 Explain the difference between deep and shallow water
waves.
 What is a tsunami?
Ocean Currents
 Ocean Currents: Continuous, directed movement of
ocean water generated by forces such as breaking waves,
wind, Coriolis Effect, tides, temperature, density and
salinity differences
 Major ocean currents are predictable – they have been
described as rivers without banks
 Types of Currents:
 Surface – 0-400 meters deep – 10% of ocean currents
 Deep – below 400 meters – 90% of ocean currents
 Three major factors set ocean currents in motion:
 Thermohaline Circulation (density driven)
 Wind Driven Circulation
 Changes in Sea Level
Thermohaline/Density Driven
Circulation
 Affect deep ocean currents
 Density differences are occur as a result of temperature and salinity.
 Warm water holds less salt than cold water so it is less dense and rises
toward the surface while cold, salt laden water sinks.
 As the warm water rises though, the cold water is forced to rise through
upwelling and fills the void left by the warm water.
 When cold water rises, it too leaves a void and the rising warm water is
then forced, through downwelling, to descend and fill this empty space,
creating thermohaline circulation.

Coldest water is at the poles and have higher salinities because of low
precipitation and the formation of sea ice
 Minute changes in density cause large changes in circulation… for this
reason, oceanographers measure density to 5 decimal places
 Demonstration http://www.divediscover.whoi.edu/circulation/demonstration.html
Wind-Driven Circulation
 Wind transfers energy to the water it blows across by
the force of friction on the water’s surface
 Winds cause both surface currents and waves
 Cause horizontal flow of water.
 If the wind blows long enough in the same direction, it
will cause a water current to develop
 What happens if the wind then stops blowing? - The
current continues to flow until internal friction, or
friction with the sea floor, dissipates its energy
Global Wind Patterns
Gyres
 Gyres: Large system of
rotating ocean currents,
particularly those involved
with large wind
movements.
 Gyres are caused by the
Coriolis Effect
 There are five major gyres:
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North Atlantic
South Atlantic
North Pacific
South Pacific
Indian
Upwelling versus Downwelling
Upwelling
Downwelling
 Upward vertical current that
 A downward vertical current
brings deep water to the surface
 Tends to bring deepwater
nutrients up into the shallow
water – increasing biological
productivity
 Sometimes upwelling occurs when
a wind blowing parallel to shore
pushes surface water out to sea
due to Ekman Transport
 Ekman Transport: The net
motion of water column down to
friction depth
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Northern Hemisphere =90o to the
right
Southern Hemisphere = 90o to the
left
that pushes surface water
deep into the ocean
 Carry nutrients and other
essential materials out to the
deep ocean – have no
dramatic effect on biological
productivity
Upwelling and Downwelling Deep Ocean
e-education.psu.edu
Coastal Upwellings and
Downwellings
eeb.ucla.edu
Eddies
 Gyres flow in a general area but they don’t flow within perfectly
defined paths… they can vary due to wind strength
 Eddies: Swirling currents
 Caused by friction with adjacent water
 Can form large circular loops that can temporarily break away:
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Cold–core eddies – flow counter clockwise in the northern hemisphere
Warm-core eddies – flow clockwise in the northern hemisphere
Both types can travel slowly for weeks, months, and even years…
 Eddies are important because:
 they can affect local temperatures and weather conditions by
redistributing heat.
 commercial fishing boats use eddies to located fish.
 they can affect ship speeds.
The Ocean Conveyor Belt
 The Ocean Conveyor Belt: The interconnected flow of
currents that redistribute heat - AKA the Earth’s Air
conditioner
 It would take one to two thousand years for a drop of water
to complete a cycle on the ocean conveyer belt…
Changes in Sea Level
 Sea level: the Average level of the sea’s surface at its mean
height between high and low tide
 Changes in sea level occur in horizontal distances
 Ocean circulation causes slopes to develop
 Ex. when a land mass interrupts a current’s flow, water
mounds up against the land
 The slope in the water surface causes a horizontal difference
in water pressure
 The water will tend to flow out due to this difference creating
a pressure gradient
 The steeper the mound of water, the larger and faster the
current will be
sealevel.jpl.nasa.gov
Importance of Ocean Circulation
 Ocean circulation affects the Earth in many ways:
 Circulates nutrients and energy throughout the ocean
 Affects the Earth’s climate
 Affects the transport and shipping industries.
 Transport living things like seeds and actual organisms
around the globe.
Studying Ocean Currents
 Different Approaches:
 Lagrangian Method (AKA the Float Method): Studies currents
by tracking and drifting an object – floating something in the
current that records information as it drifts
 Eulerian Method (AKA the Flow Method): Studies currents by
staying in one place and measuring the velocity of water as it
flows past.
 Flotsam Method: Scientists also take advantage of accidental
opportunities to study currents…
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In 1992 a cargo carrier lost its cargo – 30,000 athletic shoes while enroute to Seattle from Korea. Oceanographers asked the public to report
the time, date, and place they found the shoes…. Using this info they
were able to improve current models in the north pacific
In 1992 a ship lost 29,000 rubber ducks, frogs, and turtles while sailing
from China to Seattle. The toys washed up along the north pacific coast
at various location from Oregon to Alaska… eventually drifting through
the Bering Strait… they are expected to make it New England… none of
washed up yet.
Ocean Currents Song
 http://safeshare.tv/w/HfLljJafyJ
Day 4: Waves
 What is a wave?
 What are the three types of waves?
 What are the crest, trough, height, wavelength, period, and
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frequency of a wave?
How do wave length and period relate to a wave’s speed?
What disturbing forces cause waves?
What restoring forces resist waves?
Compare shallow water and deep water waves
What three factors affect maximum wave size?
What causes internal waves?
Wave
 Wave: Transmission of energy
through matter
 When energy moves through
matter as a wave, the matter
moves back and forth but then it
returns to its original position
 It transmits energy to the
adjacent matter (next thing)
allowing the energy to continue
 Example:
Dropping a stone in water…
Waves ripple away from the splash…
the water doesn’t move away only
the energy
Types of Progressive Waves
 Progressive Wave: Wave in which energy progresses
from one point to another
 Progressive waves are waves in which there is a
direction to the transmission of the wave
 Can be created by a variety of disturbing forces
including: wind, seismic activity, volcanic eruptions,
landslides, gravity, or a change in atmospheric pressure
 3 Types of Progressive Waves:
 Longitudinal
 Transverse
 Orbital
Longitudinal Wave
 Longitudinal Wave: Matter moves back and forth in
the same direction that the energy travels
 Can move through all states of matter
 Energy is transmitted through the compression and
decompression of particles – like a spring or slinky
 Example: Sound travels in longitudinal waves
spot.pcc.edu
Transverse Wave
 Transverse Wave: Motion of the matter is
perpendicular to the direction in which the wave as a
whole is moving
 Example: Ripple in pond
Orbital Waves
 Orbital Waves: Transmit only through fluids as
energy moves through the fluid in a circular motion as
it passes
 Waves in the ocean are orbital waves
kingfish.coastal.edu
Wave Terminology
 Wavelength: The horizontal distance between two successive crests or troughs
 Crest: Highest part of the wave
 Trough: Lowest part of the wave
 Height: Vertical distance between 2 successive crests or troughs
 Period: The time it takes for 2 troughs or 2 crests to pass a fixed point
 Frequency: The number of waves or crests/troughs that pass a fixed point each
second
 Celerity: Speed of the wave - equal to the wavelength ÷ period
outreach.phas.ubc.ca
asdk12.org
Waves and Mathematics
 Wave characteristics can be expressed mathematically
 Speed = wavelength ÷period or S = L ÷ T
 Ratio of wave height to wavelength – H:L
 Wavelength (L: Depth in meters)
 Period (T: Time in seconds)
 Speed (S: Speed in meters per second)
 Wave Height (H: Height in meters)
 Example: If in a given wave, T=20s and L=200m, what
is the speed of the wave?
S=200m ÷ 20s + 10m/s
Wave Formation
 Disturbing Forces: Forces that cause waves
 Restoring Forces: Forces that resist waves
 The intensity and duration of a disturbing force and the
interaction of restorative forces give waves their
characteristics
 Fluids tend to remain at rest – they only move when
something imparts energy on them – disturb them
 Disturbing forces that cause ocean waves include wind,
changes in gravity, and seismic activity (volcanoes and
earthquakes)
 Restorative forces include gravity, Coriolis effect, and
surface tension
Wave Classification Based on
Resisting Forces
 Capillary Waves: Primary force acting on them is
surface tension
 First to form when wind blows across still water
 Gravity Waves: Waves in which the weight of the wave
is pulled by gravity
 Most waves that concern us in oceanography are gravity
waves
Wave Patterns
 Waves tends to organize themselves into patterns
 Waves that are not organized travel at different speeds
and longer waves outrun the shorter waves… eventually
only waves of the same length are left travelling together
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Swell: The rise and fall of a uniform wave pattern on the sea
Wave Trains: Groups of swells with similar characteristics
that tend to travel together in groups
 The first wave gradually looses energy, which is picked up by
new waves forming in the trailing portion of the train
 When wave trains reach shallow water, the individual and
group speeds become the same
Waves at Different Depths
 Depth affects wave characteristics
 Deepwater Waves: Occur in water that is deeper than half their wavelength
 No interaction from the bottom can affect the wave characteristics
 Their orbital motion progresses unaffected
 Capillary waves are almost always deep water wave
 Mostly wind driven
 Transitional Waves: Occur in depths between one-half and one-twentieth the
wavelength
 At depths that are one-fourth the wavelength, the bottom of the ocean creates a
drag that affects the orbital motion –flattens the circular motion into an ellipse
 Shallow-water Waves: Occur in waters that are shallower than one-twentieth
the wavelength
 Wavelength and speed are dependent on depth, as friction with the sea floor
slows down the wave – the wave behind continues at the original speed and the
wavelength decreases – this causes the height of the wave to increase
 Waves break when they reach a height of 1:7 (height: length)
 Tides are usually shallow water waves
Waves at Different Depths
Factors Affecting Wind Wave
Growth
 Wind Speed
 Wind must be blowing faster than the wave to give it energy
 Duration
 Length of time wind blows in a single direction
 Fetch
 Surface over which the wind blows
 Large the surface area, the greater the energy transfer, the
bigger the waves
 Fully Developed Sea: Maximum wave size has been
reached (disturbing and restoring forces counterbalance)
 Rouge Wave: Theorized to result from the interaction of
two closely related wave trains
Deadliest Catch – Rogue Wave
 Rogue Wave Deadliest Catch
Interaction of Wave Trains
 In-Phase: Crest and troughs of
different trains coincide and
make larger waves
 If this happens against the
current REALLY LARGE waves
like rogue waves can form
 AKA Constructive Interference
 Out-of-Phase: Crest of one train
coincides with troughs of others
the waves cancel each other out
 This is how calm seas can
occur during strong winds
 AKA Destructive Interference
teachgreenbk.wordpress.com
Breaking Waves
 As a wave approaches shore,
the bottoms of ocean begins to
affect to orbit of the wave
 As the wave continues to move
forward the friction with the
bottom causes the wave to slow
down and the wavelength
decreases and wave height
increase
 Waves break when they reach a
height of 1:7 (height to length)
because the crest is travelling
faster than the trough making
the wave unstable and its crest
topples forward
Types of Breaking Waves
 Type of breaker depends on slope of shore and speed
 Spilling Breakers: Occur on wide flat beaches and lose
energy gradually
(longer ride for surfers)
 Plunging Breakers: Occur on narrow steep beach
slopes and loose energy faster – have a characteristic curl
(more exciting ride for surfers)
 Surging Breakers: Occur on very abrupt shores with no
opportunity for break – no surfing – very destructive
booksite.academicpress.com
Wave Deformation: Refraction
 Refraction: Bending of waves as they approach shore
at an angle
 Crest closest to shore slows sooner creating uneven
slowing and the waves refract or bend until they face the
shore more squarely slowly and evenly
answers.com
Wave Deformation: Diffraction
 Diffraction: When waves pass an obstacle and energy
shifts in the wave allowing a new wave pattern to form
past the obstacle or through an opening
 Example: Waves in well protected harbor
geographyfieldwork.com
Wave Deformation: Reflection
 Reflection: Occurs when
waves hit an obstacle and
the wave retains most of its
energy and bounces back
toward the open water
 Examples of obstacles
include cliffs or seawalls
 Can cause standing waves
– when water rocks back
and forth on the edges but
remains motionless in the
center or node (like when
you bump a cup of liquid
like a coffee cup)
Destructive Waves
 3 Types of waves are noted for their destructive power:
 Storm Surge: Destructive wave or wall of water that forms when
high winds push water up against the shore where it piles up.
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The shallower the water offshore and further it extends offshore, the
greater the surge (this is why the Gulf Coast has the biggest storm
surges) – common with hurricanes
 Seiche: Standing wave that forms in large bays and lakes as a wave
rocks back and forth
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Can result from strong winds that push water levels up one side of a bay
(this is actually common in the great lakes)
 Tsunami: Sudden water displacement caused by landslide, volcanic
eruption, iceberg calving, or most commonly an earthquake
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These are also called tidal waves (even though their not caused by tides)
Not that large at sea but as they approach shoe it becomes much higher
Tsunami
Seiche
seagrant.umn.edu
fromtheleft.wordpress.com
Storm Surge
nhc.noaa.gov
Day 5 Tides
Objectives:
 What causes tides?
 How does Newton’s Equilibrium Theory of Tides
differ from Laplace’s Dynamic Theory?
 What factors influences/affect tides?
 What are diurnal, semidiurnal, and mixed tides?
 What are tidal currents and a tidal bore?
 What are the relative positions of the sun and moon
during spring tides and neap tides?
Tides
 Tides: Daily variations in the ocean’s sea level
 Result from the gravitational pull of the moon, the
sun, and the rotation of the Earth
 Those forces pull ocean water into a huge wave with a
wavelength the size of the ocean basin (or half the
circumference of the Earth) therefore, the waves are
always shallow water and their speed is controlled by
the depth of the water
 They are “forced” waves as they are always under the
forces from which they were generated
Tides “Simplified”
 The sun and the moon create
two bulges on opposite sides
of the Earth.
 The relative positions of the
sun and moon change slowly
so the bulge rotates around
the Earth.
 As a coastline rotates into the
bulge, the tide rises – as it
rotates out, the tide falls.
science.howstuffworks.com
Tidal Theories
Equilibrium Theory
Dynamic Theory
 Proposed by Isaac Newton
 Proposed by Pierre-Simon
 The gravitational pull of the
Laplace and modified
Newton’s theory
 There are several tidal bulges
because in addition to lunar
and solar gravity the
imperfect sphere of the Earth,
the season, the time of the
month, the shape of the
ocean basin, the Coriolis
effect all influence tides.
sun and moon create two
bulges of water on either side
of the Earth.
 Assumes the Earth is
perfectly uniform, that the
water is VERY deep, and that
there are no land masses
 Problem = too simple
web.vims.edu
Tidal Patterns
 The shape and depth of the ocean
basins affect tidal patterns.
 Large wide basins tend to have a
smaller tidal range than narrow,
shallower basins.
 Diurnal Tides: Single high and low
tide daily
 Ex. Gulf of Mexico
 Semidiurnal Tides: Roughly two high
and low tides daily
 Ex. East Coast
 Mixed Tides: Two unequally high and
low tides daily
 Ex. West Coast
geocaching.com
tideclocks.com
Tidal Currents
 Daily tides create a current that flows into and out of bays,
rivers, harbors and other restricted spaces
 Inflow is called flood current
 Outtflow is called slack current
 Midpoint between high and low tide creates a slack tide
(where little water is moving)
 These currents are very important to the people in live in or
around these areas
 For example:
 large ships may only enter or leave some harbors at high tide.
 sailing vessels often use slack currents to take advantage of the flow
carrying them seaward.
Tidal Bore
 Tidal Bore: Incoming tide produces a wave that flows
into a river, bay, or other narrow opening
 This is a true “tidal wave”
 Can be several meters high
 Example: Happens in the Amazon River and Severn
River in Englad
Surfer on the
Amazon Tidal
Bore 
voyagner.com
The Sun, Moon, and Types of Tides
 Solar and lunar gravity affect the tides differently,
depending on the positions of the sun and moon relative to
the Earth
 The moon has twice the influence of the sun on the tides
 Sun has a greater gravity but is farther away than the moon
 Spring Tides: When the sun, the moon, and the Earth are in-
line it creates the highest and lowest tides

This occurs during a new moon (no moon visible) and a full moon
 Neap Tides: Weak tides created when the moon is in quarter
phase and the lines from the moon and the sun to the Earth
form a right angle.

The sun’s gravitation pulls to the side of the moon’s tidal bulge which
tends to raise the low tide and lower the high tide.
Solar and Lunar Tides
 Animation
iupui.edu
Spring Tide vs. Neap Tide
windows2universe.org